We have theoretically investigated thermoelectric (TE) effects of narrow-gap single-walled carbon nanotubes (SWCNTs) with randomly substituted nitrogen (N) impurities, i.e., N-substituted \((20,0)\) SWCNTs with a band gap of 0.497 eV. For such a narrow-gap system, the thermal excitation from the valence band to the conduction band contributes to its TE properties even at the room temperature. In this study, the N-impurity bands are treated with both conduction and valence bands taken into account self-consistently. We found the optimal N concentration per unit cell, c_opt, which gives the maximum power factor (PF) for various temperatures, e.g., PF = 0.30 W/K² m with c_opt = 3.1 × 10⁻⁵ at 300 K. In addition, the electronic thermal conductivity has been estimated, which turn out to be much smaller than the phonon thermal conductivity, leading to the figure of merit as ZT ∼ 0.1 for N-substituted \((20,0)\) SWCNTs with c_opt = 3.1 × 10⁻⁵ at 300 K.

中文翻译：

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具有随机取代杂质的窄间隙半导体碳纳米管的最佳热电功率因数

我们从理论上研究了具有随机取代的氮（N）杂质的窄间隙单壁碳纳米管（SWCNT）的热电（TE）效应 \（（（20,0）\）带隙为0.497 eV的SWCNT。对于这样的窄间隙系统，即使在室温下，从价带到导带的热激发也有助于其TE特性。在这项研究中，N-杂质带同时考虑到了传导带和价带。我们发现每单位电池的最佳N浓度c _opt，它给出了各种温度下的最大功率因数（PF），例如PF = 0.30 W / K ² m，c _opt = 3.1×10 ^-5在300 K时。据估计，它的电子热导率比声子热导率小得多，因此，N取代基的品质因数ZT约为0.1。\（（（20,0）\）在300 K下c _opt = 3.1×10 ^-5的SWCNT 。